After two long, depleting weeks on the hustings, the real work for Labour's new leader starts tomorrow.

OPINION:
Celebratory drinks drained and red balloons deflated, the day will kick off with a round of breakfast telly interviews in Auckland. From there it's a flight back to Wellington, for more interviews, and preparation for Tuesday's crunch caucus meeting.

Whether the victor is David Cunliffe or Grant Robertson, each will have their own foes to face down in that stuffy, second-floor room. Both have a set of challenges to overcome before they can even think about fighting next year's election campaign.

Expect the phone lines into Labour's offices to be scorching hot after the result is announced at 2.45pm today. Deals will be done and new alliances formed. But the old scars remain, deep and livid.

The main order of business will be selecting a deputy - assuming, of course, there is a vacancy.

Should Cunliffe win, sources say he wants Robertson to remain in the job. It would be a smart 'olive branch' gesture - one previously offered by John Key (to Bill English) and Helen Clark (to Michael Cullen).

The so-called ABC (Anyone But Cunliffe) faction notably moderated their vitriol in the last two weeks. It was assumed they were preparing the ground (and protecting their interests) in the event of a Cunliffe win.

Bloodletting will harm only the party and ensure another three years on the Opposition benches. But be serious: this is the Labour party. They have an innate compulsion to white-ant.

One sticking point is the chief whip job: currently held by Rimutaka MP Chris Hipkins. In the wake of talk of a coup against David Shearer last year, Hipkins publicly denounced the ringleader: "I think David Cunliffe has made it very difficult for the Labour Party caucus to work with him, he has undermined the leader just as he undermined the last leader."

The ABCs may choose to be conciliatory - and allow Cunliffe to fulfil the promises he made to secure votes as he campaigned. (There is a persistent rumour that Iain Lees-Galloway was offered the whips job). Alternatively those who didn't vote Cunliffe (and that is shaping up to be most of them) could put up a fight.

Cunliffe might be inclined to tear down the old guard, remove his enemies. But they are among the party's most talented and experienced. Rongotai MP Annette King is effective as well as much-loved in the party. Clayton Cosgrove has his strengths, and Trevor Mallard has valuable knowledge of the machinations of Parliament. If they are suddenly cast into the shadows, all pretence of ''unity'' will be shattered. MPs Phil Goff and Ruth Dyson, however, may however be considering their future.

None of this is to say that a Robertson win will see harmony and solidarity return to Labour. Quite aside from the ire this would ignite among the party faithful who see Cunliffe as their left-wing Messiah, the Wellington Central MP also has his detractors.

There is lingering wariness because his supporters were calculating when would be the right time to topple David Shearer. Robertson will have to carefully select his team to mollify Team Cunliffe. List MP and finance spokesman David Parker is mooted as his deputy. But a top job for Cunliffe will be expected - the same goes for candidate number three Shane Jones.

Robertson must also overcome the perception that outside of Wellington he is Mr Nobody. Should he win, he plans to turn around and head straight back out on the road again, visiting the provinces as Shearer did in 2011.